Phase 3 study finds it's not perfect, but could still prevent tens of millions of cases a year.

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TUESDAY, Oct.
18 (HealthDay News) — In an important first, a new
vaccine has been shown to cut the risk of malaria in young African children
by about half, according to research announced Tuesday.

Although the effectiveness
shown in this Phase 3 trial is far less than the near-100 percent effectiveness
often seen in childhood
vaccines for other illnesses in the West, the findings are promising,
given that malaria kills some 800,000 people in sub-Saharan Africa alone each
year.

"This potentially
translates into [the prevention of] tens of millions of cases of malaria in
children," said Dr. Tsiri Agbenyega, a principal investigator of the
trial.

Other experts agreed.

"This is really
important because it's a viable strategy against a major killer of children in
the world," added Dr. Kenneth Bromberg, chairman of pediatrics and
director of the Vaccine Research Center at the Brooklyn Hospital Center, New
York City.

This is also the first
vaccine that is successful against a parasite, in this case Plasmodium
falciparum, which causes mosquito-transmitted malaria.

The results — the
first from the Phase 3 trial — were announced Tuesday at the Malaria
Forum hosted by the Bill & Melinda Gates Foundation in Seattle, and
published simultaneously online in the New England Journal of
Medicine.

The trial was funded by
GlaxoSmithKline (GSK) Biologicals and the PATH Malaria Vaccine Initiative,
which are developing the vaccine together with African research centers.

Speaking at a news briefing
Tuesday, Andrew Witty, CEO of GSK, said he is "hopeful we're going to be
able to bring the vaccine to children in Africa perhaps as early as 2015."

The trial enrolled more
than 15,400 children from seven countries in sub-Saharan Africa in two age
groups: 6-12 weeks old and 5 to 17 months.

Children were assigned to
one of two groups, one receiving the vaccine (called RTS,S/AS01) and the other
receiving a placebo. Seventy-five percent of both groups also followed
conventional preventive measures, namely the use of insecticide-treated bed
nets in the home.

Tuesday's announcement
addressed only the results from 6,000 children in the older age group who were
followed for a year after vaccination.

For infants 5 to 17 months
old, three doses of the vaccine reduced the rate of severe malaria by 47
percent and less-severe cases, characterized by fever and chills, by 56
percent. Severe malaria can affect the blood, brain, or kidneys and can be
fatal.

The less impressive results
in regards to the more severe malaria cases was not surprising given that
similar results had been seen in the Phase 2 trial, said Agbenyega, who is also
chair of the Clinical Trials Partnership Committee, a collaboration of
scientists, academic partners and others engaged in malaria prevention.

"Obviously, one would
want to have higher efficacy [effectiveness] when it comes to severe disease,
but we're hoping we can still improve on the vaccine as we go along," he
added.

In both groups together,
the vaccine cut the rate of malaria by about 35 percent.

"To me, that means
it's less effective in younger kids," said Bromberg.

Babies, in particular, are
vulnerable to a whole host of infectious diseases, including malaria.

"Children have a
relative immune deficiency between the time they lose their antibodies from
their mother until their own immune system kicks in at 6 to 9 months,"
explained Dr. Bruce Hirsch, attending physician in infectious diseases at North
Shore University Hospital in Manhasset, N.Y. "A vaccine like this could
help bridge that gap."

While noting that the
results were "gratifying," Hirsch also cautioned that "the
efficacy rate is not 100 percent and ... these are preliminary results."

Side effects were about the
same in both groups and "were what you might typically see with other
childhood vaccines — low-grade fever
and some swelling at point of injection," said Agbenyega.

Seizures in participants
were attributed to malaria.

Data on the 6- to 12-week
age group should be available by the end of 2012, said Agbenyega.
The authors are also awaiting
30-month follow-up safety
and efficacy data by the end of 2014.

Calling the trial results a
"promising advance," the U.S. Centers for Disease Control and
Prevention said the vaccine builds on already successful efforts to beat back
malaria in poorer countries.

"The vaccine provided
this protection in settings where there is ongoing use of other effective
malaria prevention and treatment interventions: bed nets, antimalarial drugs,
indoor residual insecticide spraying to prevent mosquito-borne transmission,
and drugs to protect pregnant women and their fetuses from malaria's adverse
effects," the CDC said in a news release.

Efforts to help prevent
malaria in these ways are working, the agency said, and "many countries
have seen decreases of up to 50 percent in deaths of children younger than 5
years."

The final results of the
vaccine trial will eventually be submitted to health regulators in Europe and
elsewhere for approval. There are no plans to file for approval from the U.S.
Food and Drug Administration at this point.

According to Witty, GSK
plans to make the vaccine available "at the lowest price possible,"
with only a 5 percent profit margin, which will be reinvested into research into
malaria and "other neglected tropical diseases."

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